*::after,
*::before {
  box-sizing: border-box;
}

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
  background: #114b64;
}

.window {
  position: relative;
  width: 340px;
  height: 480px;
  background: #fff;
  border-radius: 170px;
  border: 4px solid #114b64;
  box-shadow: 0 0 0 12px #fff;
  overflow: hidden;
}

.window::after {
  content: "";
  position: absolute;
  top: 190px;
  left: calc(50% + 45px);
  width: 30px;
  height: 30px;
  border-radius: 50%;
  background: #f44336;
  animation: bounce 1s ease-in-out infinite;
}

.window .stair {
  position: absolute;
  width: 100%;
  right: calc(-100% + 0px);
  top: 100px;
  animation: stairs 1s linear infinite;
}

.window .stair span {
  position: absolute;
  top: calc(var(--i) * 40px);
  right: calc(var(--i) * 40px);
  width: 100%;
  min-height: 40px;
  background: #114b64;
  border-bottom: 4px solid #fff;
  border-top-left-radius: 4px;
}

@keyframes stairs {
  0% {
    transform: translateX(0) translateY(0);
  }
  100% {
    transform: translateX(40px) translateY(-40px);
  }
}

@keyframes bounce {
  0%,
  100% {
    transform: translateY(-1px);
  }
  50% {
    transform: translateY(-40px);
  }
}
